Development of a viable biofuel replacement for petrochemicals poses at least three challenges. The first challenge is to identify a raw material that can produce biofuels completely compatible with engines currently run on petrochemicals without the need for conversion. The second challenge is to develop a cultivation technology that can produce this raw material at a competitive cost in the volume necessary to support the current demand of diesel, gasoline, and jet fuel consumers. The third challenge is to create a biofuel industry that can eliminate the negative environmental and economic impact of petrochemical energy use without creating a host of different but equally negative results, such as competition for food crops, competition for arable land, and creation of toxic byproducts. Sugar and/or starch crops, such as sugar cane, sugar beets, sweet sorghum and corn, to produce ethanol have been researched as a viable biofuel source. Opponents of currently exploratory fuels claim that, for example, corn ethanol production does not result in a net energy gain or that the consequences of large scale ethanol production to the food industry and environment offset any potential gains from ethanol. Plants that naturally produce oil, such as oil palm, soybean, algae, and jatropha, to produce biodiesel have also been explored.
Algaculture is a form of aquaculture involving the farming of species of algae. When cultivating algae, several factors must be considered, and different algae have different requirements. The water must be in a temperature range that will support the specific algal species being grown. Nutrients must be controlled so algae will not be “starved” and so that nutrients will not be wasted. Light must not be too strong nor too weak. Algae can be cultured in open-ponds or photo-bioreactors.
Open-ponds, as the name implies, are large, exposed bodies of water in which algae is grown. They are much more vulnerable to contamination by other microorganisms, such as invasive algal species or bacteria. Because of these factors, the number of species successfully cultivated in an open-pond system for a specific purpose is relatively limited. In open systems, one does not have control over water temperature and lighting conditions. The growing season is largely dependent on location and, aside from tropical areas, is limited to the warmer months.
Algae can also be grown in a photo-bioreactor (PBR). A PBR is a bioreactor which may incorporate some type of light source. Virtually any translucent container could be called a PBR, however the term is more commonly used to define a closed system, as opposed to an open tank or pond. Because these systems are closed, all essential nutrients must be introduced into the system to allow algae to grow and be cultivated. Essential nutrients include carbon dioxide, water, minerals and light. Some PBR's operate in a “batch mode” where a container (for example, a bag) is filled with water, inoculated with a small amount of algae, allowed to grow for a period of time supplemented with nutrients, then drained from the container for harvest of the entire culture.